Light-emitting device and surface-emitting light source

ABSTRACT

According to one embodiment, the light guide plate has a first major surface, a second major surface, a side surface, and a recess. The recess is provided in the second major surface. The fluorescent layer is provided in the recess. The light-emitting element is bonded to the fluorescent layer and includes an electrode on a surface of the light-emitting element on a side opposite to a surface of the light-emitting element bonded to the fluorescent layer. The module side surface includes at least a portion of the side surface of the light guide plate. The first interconnect is provided along the second major surface and connected to the electrode of the light-emitting element. The second interconnect is provided on the module side surface and connected to the first interconnect.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2018-107084, filed on Jun. 4, 2018; theentire contents of which are incorporated herein by reference.

FIELD

This invention described herein relate to a light-emitting device and asurface-emitting light source.

BACKGROUND

A light-emitting device that uses a light-emitting element such as alight-emitting diode or the like is utilized widely in, for example, asurface-emitting light source such as the backlight of a liquid crystaldisplay, etc. For example, it is highly desirable to reduce thethickness of the surface-emitting light source in a direct-type liquidcrystal display in which the surface-emitting light source is disposedat the back surface of the liquid crystal panel.

SUMMARY

According to an embodiment of the invention, a light-emitting deviceincludes a light guide plate, a fluorescent layer, a light-emittingelement, a module side surface, a first interconnect, and a secondinterconnect. The light guide plate has a first major surface, a secondmajor surface, a side surface between the first and second majorsurfaces, and a recess. The first major surface functions as alight-emitting surface. The second major surface is located on a sideopposite to the first major surface. The recess is provided in thesecond major surface. The fluorescent layer is provided in the recess.The light-emitting element is bonded to the fluorescent layer andincludes an electrode on a surface of the light-emitting element on aside opposite to a surface of the light-emitting element bonded to thefluorescent layer. The module side surface includes at least a portionof the side surface of the light guide plate. The first interconnect isprovided along the second major surface and connected to the electrodeof the light-emitting element. The second interconnect is provided onthe module side surface and connected to the first interconnect.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a light-emitting device ofan embodiment;

FIG. 2 is an enlarged cross-sectional view of portion A in FIG. 1;

FIG. 3 is a schematic plan view of portion A of FIG. 1;

FIG. 4 is a schematic cross-sectional view of a surface-emitting lightsource of an embodiment;

FIG. 5 is an enlarged cross-sectional view of a connection portionbetween the light-emitting devices of FIG. 4;

FIG. 6 is a schematic plan view of the surface-emitting light source ofthe embodiment;

FIG. 7 is a schematic plan view of the surface-emitting light source ofthe embodiment;

FIG. 8 is a schematic plan view of the surface-emitting light source ofthe embodiment; and

FIG. 9A to FIG. 9D are schematic cross-sectional views showing a methodfor manufacturing the light-emitting device of the embodiment.

DETAILED DESCRIPTION

Embodiments will now be described with reference to the drawings. Thesame components in the drawings are marked with the same referencenumerals.

FIG. 1 is a schematic cross-sectional view of a light-emitting device 1of an embodiment.

The light-emitting device 1 includes a light guide plate 10, alight-emitting element 30, a fluorescent layer 20, a light-reflectiveresin member 60, a first interconnect 71, and a second interconnect 72.The light guide plate 10 and the light-reflective resin member 60 areincluded in a module main body 80 used as the exterior of thelight-emitting device 1.

In the example shown in FIG. 1, the light-emitting device includesmultiple light-emitting elements 30. Or, one light-emitting element 30may be included in the light-emitting device 1.

FIG. 2 is an enlarged cross-sectional view of a portion (portion A) ofthe light-emitting device 1 shown in FIG. 1 including one light-emittingelement 30.

FIG. 3 is a schematic plan view of portion A of FIG. 1. The light guideplate 10 is a member that is transmissive to the light emitted by thelight-emitting element 30 and the light emitted by the fluorescentincluded in the fluorescent layer 20, receives the light of thelight-emitting element 30 and the fluorescent layer 20, and emits thelight in a planar configuration from a first major surface 11.

For example, a thermoplastic resin such as acrylic, polycarbonate,cyclic polyolefin, polyethylene terephthalate, polyester, or the like, athermosetting resin such as epoxy, silicone, or the like, glass, etc.,can be used as the material of the light guide plate 10. Polycarbonatewhich is inexpensive and has high transparency is favorable among thesematerials.

The light guide plate 10 has a first major surface 11 used as alight-emitting surface, a second major surface 12 on the side oppositeto the first major surface 11, and a recess 15 provided in the secondmajor surface 12.

The fluorescent layer 20 is provided in the recess 15. Thelight-emitting element 30 is bonded to the fluorescent layer 20 on thesecond major surface 12 side of the light guide plate 10. The recess 15can function as the alignment portion of the light-emitting element 30with respect to the light guide plate 10.

The light-emitting element 30 has a main light-emitting surface 31 wherethe light mainly is extracted, and a pair of positive and negativeelectrodes 32 provided on the side opposite to the main light-emittingsurface 31. For example, the light-emitting element 30 includes atransparent substrate such as sapphire or the like and a semiconductorstacked structure that is stacked on the transparent substrate. Thesemiconductor stacked structure includes, for example,In_(x)Al_(y)Ga_(1-x-y)N (0≤x, 0≤y, and x+y≤1) and can emit blue light.

For example, the main light-emitting surface 31 of the light-emittingelement 30 is bonded to the fluorescent layer 20 by a transparentbonding agent. The side surface and the electrodes 32 of thelight-emitting element 30 are positioned outside the recess 15.

The fluorescent layer 20 includes a main material, and a fluorescentdispersed in the main material. For example, an epoxy resin, a siliconeresin, glass, etc., can be used as the material of the main material ofthe fluorescent layer 20. From the perspective of lightfastness and easeof forming, it is favorable to use a silicone resin as the mainmaterial.

The fluorescent is excited by the light emitted by the light-emittingelement 30 and emits light of a wavelength different from the wavelengthof the light emitted by the light-emitting element 30. For example, aYAG fluorescent, a p-sialon fluorescent, a KSF-based fluorescent, etc.,can be used as the fluorescent.

For example, the fluorescent layer 20 that includes a YAG fluorescenthaving a yellowish light emission can be used with the light-emittingelement 30 having a bluish light emission. The fluorescent layer 20 mayinclude multiple types of fluorescent materials. For example, the colorreproduction range of the light-emitting device 1 can be widened byusing the fluorescent layer 20 including a p-sialon fluorescent having agreenish light emission and a KSF-based fluorescent having a reddishlight emission with the light-emitting element 30 having a bluish lightemission.

A recess 16 is provided in the first major surface 11 of the light guideplate 10. An optical functional portion 40 is provided in the recess 16.The optical functional portion 40 is provided at a position opposing therecess 15 formed in the second major surface 12. In other words, theoptical functional portion 40 is provided at a position opposing thefluorescent layer 20 provided in the recess 15 and the light-emittingelement 30 bonded to the fluorescent layer 20. It is favorable for theoptical axis of the light-emitting element 30 and the optical axis ofthe optical functional portion 40 to substantially match. Theconfiguration of the recess 16 is, for example, an inverted polygonalpyramid such as an inverted circular cone, an inverted quadrilateralpyramid, an inverted hexagonal pyramid, etc., or an inverted truncatedcircular cone, an inverted truncated polygonal pyramid, etc.

The optical functional portion 40 is a transparent resin, glass, air, orthe like that has a lower refractive index than the light guide plate 10and can function as a lens widening the light in the planar direction ofthe light guide plate 10 by refracting the light at the interfacebetween the light guide plate 10 and the optical functional portion 40.

A light-scattering layer 50 that includes a light-scattering agent isprovided on the upper surface of the fluorescent layer 20. Thelight-scattering layer 50 scatters a portion of the light emitteddirectly upward from the light-emitting element 30 and returns a portionof the light downward. Thereby, the region of the first major surface 11of the light guide plate 10 which is the light-emitting surface of thelight-emitting device 1 can be suppressed from being too bright at thevicinity directly above the light-emitting element 30 compared to theother regions.

The light guide plate 10 has a side surface 13 that continues from thefirst major surface 11 and forms a substantially right angle with thefirst major surface 11. The light guide plate 10 also has a tiltedsurface 14 continuing from the second major surface 12 and forming anobtuse angle with the second major surface 12. The tilted surface 14 andthe second major surface 12 are covered with the light-reflective resinmember 60. Therefore, the light that travels through the light guideplate 10 toward the tilted surface 14 and the second major surface 12can be reflected by the light-reflective resin member 60 and orientedtoward the first major surface 11.

The light-reflective resin member 60 covers the side surface of thelight-emitting element 30. Therefore, the light that is emitted from theside surface of the light-emitting element 30 can be reflected by thelight-reflective resin member 60, oriented toward the mainlight-emitting surface 31 of the light-emitting element 30, andintroduced to the fluorescent layer 20 from the main light-emittingsurface 31. The light-reflective resin member 60 is insulative and sealsthe electrodes 32 of the light-emitting element 30.

The light-reflective resin member 60 is reflective to the light emittedby the light-emitting element 30 and the light emitted by thefluorescent layer 20 and is, for example, a resin including a whitepigment, etc. In particular, it is favorable for the light-reflectiveresin member 60 to be a silicone resin including titanium oxide.

The light-reflective resin member 60 includes a first light-reflectingportion 61 provided on the tilted surface 14 of the light guide plate10, and a second light-reflecting portion 62 provided on the secondmajor surface 12 of the light guide plate 10.

The first interconnect 71 is provided on the lower surface of the secondlight-reflecting portion 62 along the second major surface 12. The firstinterconnect 71 is connected to the electrodes 32 of the light-emittingelement 30. In the case where the light-emitting device 1 includes themultiple light-emitting elements 30, the first interconnect 71 connectsthe electrodes 32 of mutually-adjacent light-emitting elements 30 toeach other as shown in FIG. 1.

A module side surface 81 of the module main body 80 including the lightguide plate 10 and the light-reflective resin member 60 includes atransparent portion 17 and the first light-reflecting portion 61 of thelight-reflective resin member 60.

The transparent portion 17 includes the side surface 13 provided on thefirst major surface 11 side of the light guide plate 10. The firstlight-reflecting portion 61 is provided on the second major surface 12side of the transparent portion 17.

The second interconnect 72 is provided on the first light-reflectingportion 61 of the module side surface 81; and the second interconnect 72leaves the transparent portion 17 exposed. The second interconnect 72 isconnected to the first interconnect 71 on the lower surface side of thelight-reflective resin member 60.

The first interconnect 71 and the second interconnect 72 are, forexample, a metal film formed as one body by sputtering. The firstinterconnect 71 and the second interconnect 72 include, for example,copper, gold, silver, aluminum, etc.

The multiple fluorescent layers 20, the multiple light-scattering layers50, and the multiple optical functional portions 40 are provided tocorrespond respectively to the light-emitting elements 30 in the casewhere the light-emitting device 1 includes the multiple light-emittingelements 30.

A surface-emitting light source that has a wider light emission surfacearea can be configured by multiply combining the light-emitting device 1shown in FIG. 1.

FIG. 4 is a schematic cross-sectional view of a surface-emitting lightsource 100 of an embodiment.

FIG. 5 is an enlarged cross-sectional view of the connection portionbetween the light-emitting devices 1 of FIG. 4.

The multiple light-emitting devices 1 are arranged to cause the moduleside surfaces 81 to be adjacent to each other. The second interconnects72 that are formed on the module side surfaces 81 of the adjacentlight-emitting devices 1 are connected to each other directly or via aconductive material. For example, the second interconnects 72 can bedirectly bonded to each other by applying heat and mechanical pressure.Or, the second interconnects 72 can be bonded to each other by aconductive material such as a conductive paste, etc.

The transparent portions 17 are bonded to each other at the module sidesurfaces 81. Because the transparent portions are provided at theboundary between the adjacent light-emitting devices 1 on thelight-emitting surface side of the surface-emitting light source 100 andbecause the second interconnects 72 are not provided on the transparentportions 17, the boundary between the light-emitting devices 1 is notdark; and a brightness and a color that are uniform in the planardirection can be obtained.

In the case where the transparent portions 17 at the side surfaces ofthe light-emitting devices 1 protrude further than the secondinterconnects 72, a gap may be formed between the adjacent secondinterconnects 72. In such a case, the second interconnects 72 can beelectrically connected to each other by providing a conductive materialin the gap between the second interconnects 72.

Or, in the case where a gap is formed between the adjacent transparentportions 17 in the state in which the second interconnects 72 are bondedto each other, the luminance at the boundary between the light-emittingdevices 1 may be reduced if foreign matter enters the gap. Therefore, inthe case where the gap is formed between the adjacent transparentportions 17, it is desirable to provide a light-transmissive material (aresin or glass) in the gap.

FIG. 6 and FIG. 7 are schematic plan views of the surface-emitting lightsource 100.

One light-emitting device 1 is formed in a configuration that isquadrilateral or has four sides when viewed in plan. The four sidescorrespond to the side surface of the light-emitting device 1. In theexample shown in FIG. 6, the second interconnects 72 are provided at twoopposing sides of the four sides of the light-emitting device 1. Thesecond interconnect 72 is provided partially over one side but does notextend over the entire one side.

In the example shown in FIG. 6, for example, two light-emitting devices1 a and 1 b are electrically connected to each other via the secondinterconnects 72. One second interconnect 72 of the one light-emittingdevice 1 a is connected to an anode terminal A. The other secondinterconnect 72 of the one light-emitting device 1 a is connected to onesecond interconnect 72 of the other light-emitting device 1 b. The othersecond interconnect 72 of the other light-emitting device 1 b isconnected to a cathode terminal C. In other words, the multiplelight-emitting devices 1 a and 1 b are directly connected between theanode terminal A and the cathode terminal C via the second interconnects72 provided on the side surfaces.

In the example shown in FIG. 7, the surface-emitting light source 100includes, for example, the four light-emitting devices 1 a, 1 b, 1 c,and 1 d arranged in a matrix configuration. The light-emitting device 1a and the light-emitting device 1 b are connected in series to eachother. The light-emitting device 1 c and the light-emitting device 1 dare connected in series to each other. The light-emitting device groupthat includes the light-emitting device 1 a and the light-emittingdevice 1 b and the light-emitting device group that includes thelight-emitting device 1 c and the light-emitting device 1 d areconnected in parallel between the anode terminal A and the cathodeterminal C.

One light-emitting device 1 includes the two second interconnects 72provided along two corner portions at mutually-diagonal positions. Onesecond interconnect 72 of the two second interconnects 72 is connectedto the second interconnects 72 of other light-emitting devices 1 in thelateral direction and the longitudinal direction of the matrix array.The other second interconnect 72 is connected to an external terminal(the anode terminal A or the cathode terminal C).

In the light-emitting device 1 of the embodiment, because thelight-emitting element 30 is mounted in the light guide plate 10, thedistance between the light guide plate 10 and the light-emitting element30 can be small; and a thinner light-emitting device 1 is possible.

Further, because the connection between the adjacent light-emittingdevices 1 and the connection to the outside is formed via the secondinterconnects 72 provided on the module side surfaces 81, a wiringsubstrate is unnecessary on the second major surface 12 side of thelight guide plate 10, which is advantageous for realizing a thinnerdevice.

Because the fluorescent layer 20 is provided not on the first majorsurface 11 which is the light-emitting surface of the light guide plate10 but on the second major surface 12 side on the side opposite to thefirst major surface 11, the light that undergoes wavelength conversionin the fluorescent layer 20 can be diffused in the planar direction bythe light guide plate 10 and the optical functional portion 40; anduneven color in the surface of the light guide plate 10 can besuppressed.

For example, the light-emitting device 1 and the surface-emitting lightsource 100 of the embodiment can be used in the backlight of a liquidcrystal display. For example, in a direct-type liquid crystal display inwhich the backlight is disposed at the back surface of the liquidcrystal panel, the distance between the liquid crystal panel and thelight-emitting device is short; therefore, uneven color of thelight-emitting device easily causes uneven color of the liquid crystaldisplay. Therefore, the uneven color of the liquid crystal display canbe reduced by using, as the backlight of the direct-type liquid crystaldisplay, the light-emitting device 1 and the surface-emitting lightsource 100 such as those of the embodiment that have low uneven color.

FIG. 8 is a schematic plan view of another example of thesurface-emitting light source 100.

The surface-emitting light source 100 includes, for example, the fourlight-emitting devices 1 a, 1 b, 1 c, and 1 d arranged in a matrixconfiguration.

The light-emitting device 1 a includes two second interconnects 72provided along two corners positioned at the two ends of the same oneside; one of the two second interconnects 72 is connected to a terminal91; and the other of the two second interconnects 72 is connected to aterminal 92.

The light-emitting device 1 b includes two second interconnects 72provided along two corners positioned at the two ends of the same oneside; one of the two second interconnects 72 is connected to theterminal 92; and the other of the two second interconnects 72 isconnected to a terminal 93.

The light-emitting device 1 c includes two second interconnects 72provided along two corners positioned at the two ends of the same oneside; one of the two second interconnects 72 is connected to theterminal 91; and the other of the two second interconnects 72 isconnected to a terminal 94.

The light-emitting device 1 d includes two second interconnects 72provided along two corners positioned at the two ends of the same oneside; one of the two second interconnects 72 is connected to theterminal 94; and the other of the two second interconnects 72 isconnected to the terminal 93.

The second interconnect 72 of the light-emitting device 1 a connected tothe terminal 92 and the second interconnect 72 of the light-emittingdevice 1 b connected to the terminal 92 are bonded to each other betweenthe side surface of the light-emitting device 1 a and the side surfaceof the light-emitting device 1 b.

The second interconnect 72 of the light-emitting device 1 c connected tothe terminal 94 and the second interconnect 72 of the light-emittingdevice 1 d connected to the terminal 94 are bonded to each other betweenthe side surface of the light-emitting device 1 c and the side surfaceof the light-emitting device 1 d.

Only the light-emitting device 1 a can be switched ON by causing acurrent to flow between the terminal 91 and the terminal 92.

Only the light-emitting device 1 b can be switched ON by causing acurrent to flow between the terminal 92 and the terminal 93.

Only the light-emitting device 1 c can be switched ON by causing acurrent to flow between the terminal 91 and the terminal 94.

Only the light-emitting device 1 d can be switched ON by causing acurrent to flow between the terminal 94 and the terminal 93.

All of the light-emitting devices 1 a, 1 b, 1 c, and 1 d can be switchedON by causing a current to flow between the terminal 91 and the terminal93.

FIG. 9A to FIG. 9D are schematic cross-sectional views showing a methodfor manufacturing the light-emitting device 1 of the embodiment.

First, the light guide plate 10 is prepared as shown in FIG. 9A.

For example, the light guide plate 10 can be formed by injectionmolding, transfer molding, thermal transfer, etc. The alignmentprecision between the optical functional portion 40 and thelight-emitting element 30 can be high by using a mold to collectivelyform the recess 16 where the optical functional portion 40 is providedand to form the recess 15 which is used as the alignment portion of thelight-emitting element 30 and is where the fluorescent layer 20 isprovided.

As shown in FIG. 9B, the light-scattering layer 50 is provided on thebottom surface of the recess 15. For example, the light-scattering layer50 can be formed by a method such as potting, printing, spraying, etc.

As shown in FIG. 9C, the fluorescent layer 20 is provided on thelight-scattering layer 50 inside the recess 15. For example, thefluorescent layer 20 can be formed by a method such as potting,printing, spraying, etc.

As shown in FIG. 9D, the light-emitting element 30 is disposed on thefluorescent layer 20. The main light-emitting surface 31 of thelight-emitting element 30 is bonded to the fluorescent layer 20.

Subsequently, the optical functional portion 40 described above may beprovided in the recess 16 on the first major surface 11 side of thelight guide plate 10. Further, the light-reflective resin member 60 isprovided to cover the second major surface 12 and the tilted surface 14of the light guide plate 10.

The processes may proceed up to this point in the wafer or panel state;subsequently, dicing may be performed at the appropriate location asnecessary.

Then, the first interconnect 71 and the second interconnect 72 areformed as one body by forming, for example, a metal film by sputteringon the side surface of the light-reflective resin member 60 and thelower surface continuing from the side surface that are exposed by thedicing.

The embodiments of the present invention have been described withreference to specific examples. However, the present invention is notlimited to these specific examples. Based on the above-describedembodiments of the present invention, all embodiments that can beimplemented with appropriately design modification by one skilled in theart are also within the scope of the present invention as long as thegist of the present invention is included. Besides, within the scope ofthe spirit of the present invention, one skilled in the art can conceivevarious modifications, and the modifications fall within the scope ofthe present invention.

What is claimed is:
 1. A light-emitting device, comprising: a lightguide plate having a first major surface, a second major surface, a sidesurface between the first and second major surfaces, and a recess,wherein the first major surface functions as a light-emitting surface,the second major surface is located on a side opposite to the firstmajor surface, and the recess is provided in the second major surface; afluorescent layer provided in the recess; a light-emitting elementbonded to the fluorescent layer, wherein the light-emitting elementincludes an electrode on a surface of the light-emitting element on aside opposite to a surface of the light-emitting element bonded to thefluorescent layer; a module side surface including at least a portion ofthe side surface of the light guide plate; a first interconnect providedalong the second major surface and connected to the electrode of thelight-emitting element; and a second interconnect provided on the moduleside surface and connected to the first interconnect.
 2. The deviceaccording to claim 1, wherein the module side surface includes: atransparent portion including a portion of the side surface of the lightguide plate provided adjacent to the first major surface side of thelight guide plate; and a first light-reflecting portion provided on thesecond major surface of the light guide plate.
 3. The device accordingto claim 2, wherein the second interconnect is provided on the firstlight-reflecting portion and leaves the transparent portion exposed. 4.The device according to claim 1, further comprising a secondlight-reflecting portion provided on the second major surface of thelight guide plate, the first interconnect being provided on the secondlight-reflecting portion.
 5. The device according to claim 4, whereinthe second light-reflecting portion covers a side surface of thelight-emitting element.
 6. The device according to claim 1, furthercomprising an optical functional portion provided at a position opposingthe recess at the first major surface of the light guide plate, arefractive index of the optical functional portion being lower than arefractive index of the light guide plate.
 7. A surface-emitting lightsource, comprising a plurality of the light-emitting devices accordingto claim 1 arranged such that the module side surfaces are adjacent toeach other, wherein the second interconnects of the adjacentlight-emitting devices are connected to each other directly or via aconductive material.